The influence of oxygen vacancy concentration in nanodispersed non-stoichiometric CeO2-δ oxides on the physico-chemical properties of conducting polyaniline/CeO2 composites

Abstract

Cerium oxide (CeO2-δ) ultrafine nanoparticles, with the lower (CeO2-δ-HT) and higher (CeO2-δ-SS) fraction of oxygen vacancies, were used as anchoring sites for the polymerization of aniline in acidic medium. As a result, polyaniline-emeraldine salt (PANI-ES)-based composites (PANI-ES@CeO2-δ-HT and PANI-ES@CeO2-δ-SS) were obtained. The interaction between CeO2-δ and PANI was examined by FTIR and Raman spectroscopy. The PANI polymerization is initiated via electrostatic interaction of anilinium cation and Cl− ions (adsorbed at the protonated hydroxyl groups of CeO2-δ), and proceeds with hydrogen and nitrogen interaction with oxide nanoparticles. Tailoring the oxygen vacancy population of oxide offers the possibility to control the type of PANI-cerium oxide interaction, and consequently structural, electrical, thermal, electronic and charge storage properties of composite. A high capacitance of synthesized materials, reaching ∼294 F g−1 (PANI-ES), ∼299 F g−1 (PANI-ES@CeO2-δ-HT) and ∼314 F g−1 (PANI-ES@CeO2-δ-SS), was measured in 1 M HCl, at a common scan rate of 20 mV s−1. The high adhesion of PANI with cerium oxide prevents the oxide from its slow dissolution in 1MHCl thus providing the stability of this composite in an acidic solution. The rate of electrochemical oxidation of emeraldine salt into pernigraniline was also found to depend on CeO2-δ characteristics.